Tubular forging and process for making the same



J. MCF. SYLVESTER.

TUBULAR FORGING AND PROCESS FOR MAKING THE SAME.

APPLICATlON FILED AUG. 12 I920.

1,437,690, Patented Dec. 5, 1922.

l atented llleci 5, i922.

STATES" ear star oral-ice,

JOHN MGFALL SYLVESTER, OF ROSEMQNT, PENNSYLVANIA, ASSIGNOR TO BETHLEHEMSTEEL COMPANY, 0E BETHLEHEM, PENNSYLVANIA, A CORPORATION OF PENNSYL-VANIA.

TU -IBULAR FORGING AND PRQCESS FOR MAKING THE SMEE.

Application filed Augnstm, 1920. Serial No. 402,957.

T 0 all whom it may concern Be it known that l, vEs'rEn, a citizen ofthe United States, and residing at Rosemont, Lehigh County. State .ofPennsylvania, have invented certain new and useful Improvements inTubular Forgings and Processes for Making the Same, of which thefollowing is a specification.

My invention relates to an improved process of making tubular steelforgingsof large diameter with relatively thin walls and to the articleproduced thereby. It has reference particularly to the manufacture oftubular forgings used in making air-flasks for naval torpedoes.

. My invention finds its particular value and utility in the productionof large tubular steel torgings with relatively thin walls having anoutside diameter of at least 18 inches and a length of not less than sixfeet. it will be described with special reference to themanui acture ofa 21 naval torpedo airflask forging which forgings have an outsidediameter of about 22 inches and a length of about 13 feet and wallsapproximately 23 thick.

in the processes heretofore employed for the manufacture of navaltorpedo air-flask iorgings, considerable loss waste of maresults. one ofsuch prior process a cylindrical steel i et is cast and er certain partsare cu to remove elective material produced in casting, got is boredlongitudinally of its axis he resultant tubular o is forged v orlzed insections he er or press. ctions being heated to each for;- operation.The finished for ng is then ii machined to the required dimensions. caseof a 21" naval torpedo air lash this process results in the producughmachined weighing lbs. irom an original ingot weigaing ap roximately22,500 lbs. or a net yield in finished product of only 12% of theoriginal weight or material employed.

4 solar steel ingot is cast and rol In another process a re b led intoform of a rectangular plate which, after certain parts are discarded. issheared into two portions, each of which is then cross-relied into anapproximately square plate. roin each of these plates a cir ular blan iscut and such lanlrs are then dished or and drawn JOHN MCFALL Syn must besubjected.

- considerable scale finds its way into the finforging. lln order to cupthe circular blanks and draw them into final form, this process requiresrepeated passage of the blanks through dies and the use of punches ofdifferent diameter in the various passes. Approximately eleven passesare necessary, and repeated reheating of the forging is also required.In the case of 21" naval air-flask forgings this process has been foundto result in the production of two forgings of 2700 lbs. each romanoriginal ingot of approximately 34,000 lbs, or a net yield oi only about16%.

In both of the processes above described much loss of material thereforeoccurs by the fact that portions of the ingot or blank must be bored orcut away causing unavoidable loss of material and further loss isoccasioned by the formation. of scale during the repeated beatings towhich the forging 7 Such scale must be removed to obtain aperiectproduct which is difiiculu; to accomplish where numerous reheatings arenecessary with "the result that islied product causing the formation offorgings which are defective and lack uniformity. Furthermore, defectssuch as spurs. cold shuts, laps etc. are common in forgings produced inthe hammer or press 8 forging process. while laminations common inforginggs produced the rolling process. And addition to foregoingdefects, it is found that necessary in prior processes, reases thepercentage of unacceptable precinct on count of overheating orunderheating which are apt to occur and in general by working the metalimproper teinoeratures.

By the process my invention no cutting" g5 away of the metal isnecessary. material usually discarded fro ingot and only a limitd'nvbeatings is required. with a forging of a. given duced from a muchmaller in."

than is possible with former processes referred to. By my process lobtain in the case of a 21 n air-flask forging, a finished to ingapproximet iy 2700 lbs. fr weighing 10.500 ibs, which a net yield ofapproximately as m ingots may be employed to produce forgings of a givenweight.

Furthermore, it has been found that tubular forgings produced accordingto my invention possess few if any of the defects due to the presence ofscale and that they are uniformly free from defects such as spurs. coldshuts, laps and 'laminations. And in addition to being free from suchdefects, these forgings, as will later appear, possess qualities muchsuperior to those produced by former processes.

in the drawings accompanying this specification and forming a partthereof, 1 have illustrated in a diagrammatic way the opera tionsinvolved in producing a torpedo airflask forging according to myimproved process.

Referring to the drawings in detail:

Figure 1 illustrates an ingot of metal from which the forging is tobemade;

Figure 2 shows the ingot with the upper portion of the same cut away toeliminate defective material;

Figure 3 illustrates diagrammatically the operation of upsetting theingot;

Figure l villustrates in a more or less diagrammatic way the operationof partially piercing the ingot igure 5 is a diagrammatic View showing astep in the operations of drawing the ingot after it has been subjectedto the operations previously referred to; and

Figure 6 is a view similar to Figure 5 illustrating a further step inthe drawing operation.

In the practice of my invention as applied to the production of a navaltorpedo airfiask forging, I first cast a steel ingot from metal havingapproximately the following chemical composition:

0 Mn. P. s. Ni. 0:. Si.

25 to 55 .15 to .so% 415% 04% 1.0 m 3.0 .60 m 2.0 20

In producing air-flask forgings of the kind mentioned, it is necessaryto cast an ingot approximately 30" in diameter and weighingapproximately 10,500 pounds, and I prefer to use for that urpose an ironmold. 'Heretofore, cylin rical ingots of more than 20" in diameter havenever been cast in an: iron mold and it has been thought impracticableor impossible to cast ingots of that size in such a mold. However, Ihave found that this can be done by pouring the metal at a slow rate andby em ployin molds having extremely thick walls at the% ottom, taperingto thinner walls at the top and by using a stool having a deep concaveportion. Cylindrical in ots so cast are particularly adapted fort esubsequent operationsof my process. The term :nasaeeo cylindrical asused herein is intended to include ingots having a slight taper as wellas those of true cylindrical form.

In practicing my invention ingots may be used in which the exteriorsurface is provided with flutes or corrugations but forgin s made fromsuch ingots are not as satisfactory as those made from cylindricalingots. lhis is due to the fact that in the upsetting and piercingoperations hereinafter described difiiculty is experienced in fillingout the die. The metal at the root of the corrugationsis thus workedless than other portionswhich results in lack of uniformity in the metalof the forging. ingots cast in sand or in sand-lined molds also may beem loyed but such ingots are apt to "be contaminated by the presence ofsand cylindrical ingot B as shown in Figure 2 of.

the drawing.

After the discard is cut therefrom the ingot B is reheated to atemperature from 900 C. to 1200 C. and it is then placed in a dieillustrated at C in Figure 3 which'is somewhat larger in diameter thanthe diameter of the ingot as will appear from the dotted lines in saidfigure, such dotted linesrepresenting the size of the ingot beforefurther treatment. The inner wall of the die. while approximatelycylindrical in shape tapers slightly, thegreater diameter being at thetop. While in the die C the ingot is compressed or upset by means. of aflat punch D which is operated from any suitable source of power such asa hydraulic press. The diameter of the punch 1) is slightly less thanthe top diameter of the die. understood that after the upsettingoperation is completed the ingot is enlarged radially so that it assumesthe shape of the die C as shown by the solid lines in said Figure 3.This upsetting operation refines and compresses and densifies the metalto a considerable extent and improvesits structure so that in thesubsequent operations of drawing the metal, the development ofdefects onthe surface of the forging is largely prevented. While the ingot isstill confined in the die C and preferably without being reheated, it ispartially pierced by a piercing punch E as diagrammatically illustratedin Figure 4 of the drawing, this punch being slightly It will be 4aasaeeo tapered. lhe punch E is also operated by a hydraulic press orfrom any other suitable source of power. The ingot is pierced to such adepth as to leave a bottom disc F in the ingot of sufiicient thicknessto withstand the pressure exerted thereon by the drawing punch duringthe drawing operations hereinafter described;

' The operation of piercing the ingot causes the metal to flow in adirection generally opposite to the direction of travel of the punch asshown at G in Figure l, and in addition to partially piercing the ingot,this operationi'urther works the inner and outer surfaces of the piercedingot and also ma terially compresses, works and refines the crystallinestructure of the metal throughout the ingot.

The operation of piercing the ingot produces what will hereinafter betermed a cupped blank, this blank in the case of air-flask forgingshaving an internal diameter or" approximately 16 and a cylindrical wallapproximately 6 thick.

lhe cupped blank is now removed from the die slightly reheated,preferably to a temperature from 900 to 1200 C. and is placed on a punchH of a draw bench diagrammatically illustrated in Figure 5 of thedrawing. The cradle of the draw bench has three or four circular dies Icentered on the path of the axis of the punch H, each successwe diebeing of smaller diameter than i the preceding one. In the case ofair-flask Gill forgings, the stroke of the punch should be approximately35 feet. The cupped blank is passed through all the dies of the series,each die in turn reducing the overall diameter of the blank. .The blankis again slightly reheated and given a pass through a second set ofcircular dies of smaller diameter than those of the first set and after.being again reheated, it is passed through a third set of dies smallerin diameter than those of the second set. Each successive die in thesecond and third sets is also preferably smaller than the preceding die.

A single draw punch H may be used for the three sets 0 dies, this punchbeing slightly tapered to facilitate stripping and the diameter andtaper thereof being substantially the same as the taper and diameterofthe piercing punch E heretofore described. The draw punch is preferablyprovided with means tor stripping the blank from the punch and the.blank is stripped after each drawing operation. After the third passthrough the drawing dies, the bottom disc F is discarded and theresulting tube is'rough machined to the required dimensions, giving asheretofore noted, a rough machined 21 naval torpedo air-flask forgingweighing approximatel 2700 lbs. from an ingot weighing. 10,500 1 s. or anet yield of approximately 26%.

rI-r y During the foregoing drawing operations the cylindrical wall or"the blank, in the case of torpedo air-fiask torgings, is-re-- to theart. These operations result in working the metal so that the same iscompressed and refined and densified throughout resulting in a forginghaving a uniform grain and a compact, V homogeneous structurethroughout, and which. is practically free from the defects found in.iorgings produced by rior processes. My process therefore resu ts in asuperior product and at the same time requires less metal to produce aforging of a given weight.

flask 'forgings are exceedingly rigid and heretofore great difiicultyhas been experienced by manufacturers in producingforgings of sufficientstrength and uniformity] of structure to meet such requirements, A veryhigh percentage of such forgings have heretofore been rejected by theGovernment because of their failure to meet the standard required. Withmy process such diliiculty is practically obviated. The forgings made bythis process possess properties which fully meet the Governmentrequirements and practically one hundred per cent of the forgings thusmade are found to be acceptable.

While the invention has been described with special reference to theproduction of naval torpedo air-flask forgings. it is obviouslyapplicable for the production of large size tubular forgings for anypurpose and it is not therefore intended to limit the inlhe requirementsfor naval-torpedo airinc vention to forgings adapted for use asairfiasks for torpedoes.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is: p

1. A process of making torpedo air flask forgings which consists of thefollowing operations substantially, as described, upsetting acylindrical ingot in a confining die, partially piercing said ingot toform a cupped blank,drawing said blank through a series of dies, therebyreducing its overall diameter, all of said operations being performedwhile the metal is in a heated condition.

2. A process of making naval torpedo air flask forgingsconsisting inconfining a solid cylindrical ingot of, steel in a die closelysurrounding the same, forcing a plunger into ice said die to partiallypierce the ingot and form acupped blank and drawing said blank throughorder dies to elongate the same.

3. A torpedo air flask forging made by casting a cylindrical ingot,partially piercing the same to form a blank and drawlng the blankthrough a series of dies to reduce its overall diameter.

4. A torpedo air flask forging made by upsetting a cylindrical ingot ina. confining die, partially piercing the ingot to form a got to form acupped blank and drawing the blank through a series of dies to reduceits overall diameter.

In testimony whereof I afiix my signature.

JOHN llIoFALL SYLVESTER.

